i need the best hepa air filter help?

i have allergy and astmah, and possibly desperatly need one. replace one that is 10+ years old, as they might not make the filters anymore

It can’t be to big. large is not an option, it cannot take up half my room.

http://www.air-purifiers-america.com/category.asp?subcat=Air-Purifiers&fl=Asthma&linkid=leftMenu&search=&sortby=criteria2hitolo

i don’t know